TABLE 2.

Kinetic parameters for TEM-87 β-lactamasea

AntibioticKm (μM)kcat (s−1)kcat/Km (M−1 · s−1)
Benzylpenicillin6.2b396.3 × 106
Ampicillin5.5b183.3 × 106
Carbenicillin1.5b6.74.5 × 106
Piperacillin14705.0 × 106
Cefazolin54132.4 × 105
Nitrocefin16311.9 × 106
Cefotaxime532.24.1 × 104
Ceftazidime94232.4 × 105
Cefepime234.41.9 × 105
Aztreonam505.31.1 × 105
  • a Data for individual kinetic parameters are mean values of three measurements. Standard deviations were always lower than 10%.

  • b The Km values for benzylpenicillin, ampicillin, and carbenicillin were calculated both as Kis and by analyzing complete hydrolysis time courses (5), as described in the text. Data represent averages of the results obtained with the two methods.